The costume is super cute. We ordered the 0-6 months size (xsmall). Our little guy was 3 months when he wore it. Unfortunately it was huge on him. The size most likely should be 4 - 6 months. But the costume is super cute. Also, it most likely would be better on a cool night as it is a very warm material.

Bought this for my son for Halloween. He's a big boy and I was worried that he would grow out of it before Halloween (purchased it in August) but it's so roomy that it will likely fit him next year as well. And it has lots of room for extra layers underneath in case of a cold Halloween. It's absolutely perfect. :)